Electrical resistors – Resistance value responsive to a condition – Current and/or voltage
Reexamination Certificate
1999-12-30
2001-05-15
Easthom, Karl D. (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Current and/or voltage
C338S320000, C338S195000, C338S023000, C338S048000
Reexamination Certificate
active
06232868
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a hybrid circuit arrangement having a resistance layer applied on at least one side of a plate-shaped substrate of glass or ceramic, and having at least one overload protection arranged on the substrate that is electrically connected to the resistance layer.
Such a hybrid circuit arrangement is known, for example, from German Utility Model DE 93 19 473. Such hybrid circuits with film resistors are particularly utilized as a drop resistor or, respectively, feed resister networks in telecommunication systems and are usually manufactured in thick-film or thin-film technology. Since architectures on an integrated circuit basis have replaced the traditional architectures on the basis of transformers in the meantime, such telephone systems are currently more sensitive than ever to over-voltage and over-current risks in telephone lines. These overload risks can have many different causes, for example lightening strikes, surge voltages induced by neighboring high-tension lines or a direct coupling to high-tension lines.
As disclosed in the aforementioned utility model, thermal fuses are utilized as protection against excessively high long-duration loads, these being fastened such that the dissipated power occurring in case of overload leads to a melting of a solder location at which, for example, a spring clip of the fuse is soldered fast, so that the spring clip soldered fast with prestress snaps away and, thus, interrupts the circuit. Such thermal fuses are in fact cost-beneficial; however, a replacement of the entire hybrid circuit is necessary after a response of the fuses. In regions wherein more outages occur due to a relatively poor infrastructure of the energy and communication networks, an outlay that can no longer be justified quickly results.
SUMMARY OF THE INVENTION
An object of the present invention is thus to create hybrid circuits of the species initially cited with a protection system that is less involved even under the conditions of a relatively high overload rate and, potentially, under other specific conditions prescribed by the employment in telecommunication networks.
Given a hybrid circuit of the species initially cited, this is inventively achieved in that the fuse is formed by a PTC resistor (positive temperature coefficient resistor).
PTC resistors are non-linear resistors (ceramic semiconductors having an extremely high positive temperature coefficient (PTC). Externally or intrinsically heated PTC resistors are utilized for certain switching and regulating jobs. Due to their electrical and mechanical properties and their tolerances, however, they cannot be universally utilized. Inventively, PTC resistors are utilized in the initially cited hybrid circuit arrangement as resettable protection elements in order to enhance the safety and dependability of the systems into which the hybrid circuits are integrated and in order to lower the maintenance costs. When an overload error occurs, the resistance of the PTC resistor rises very rapidly from a basis of, for example, 25&OHgr;, i.e. within a few seconds, to a significantly higher resistance that isolates the fault. After the elimination of the fault condition and the over-voltage, the PTC resistor automatically resets itself, and, given a renewed malfunction, can again become high-impedance due to the thermal contact to the loaded film resistors (outside heating) or directly due to its own dissipated power.
For a better understanding of the invention and its developments, exemplary embodiments are described below with reference to the drawings.
REFERENCES:
patent: 4041440 (1977-08-01), Davis et al.
patent: 4222024 (1980-09-01), Ekowicki
patent: 4467310 (1984-08-01), Jakab
patent: 5166658 (1992-11-01), Fang et al.
patent: 5351026 (1994-09-01), Kanbara et al.
patent: 5436609 (1995-07-01), Chan et al.
patent: 5594407 (1997-01-01), Caddock, Jr.
patent: 5726623 (1998-03-01), Camp
patent: 6020809 (2000-02-01), Miyazaki et al.
patent: 1 253 332 (1967-11-01), None
patent: 82 13 333 U (1982-08-01), None
patent: 41 43 095 (1993-04-01), None
patent: 93 19 473 U (1994-08-01), None
patent: WO 89/03162 (1989-04-01), None
Easthom Karl D.
Schiff & Hardin & Waite
Tyco Electronics Logistics AG
LandOfFree
Hybrid circuit arrangement with overload protection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hybrid circuit arrangement with overload protection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hybrid circuit arrangement with overload protection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560467